Whales, despite their aquatic existence, are mammals that breathe air, making them susceptible to drowning. Unlike fish that extract oxygen from water through gills, whales possess lungs and must regularly surface to inhale atmospheric air. Drowning for a whale occurs when it is unable to reach the water’s surface to breathe, leading to suffocation. Various factors can compromise a whale’s ability to access air, leading to a fatal outcome.
Why Whales Are Susceptible
Whales are fully aquatic mammals whose respiratory system operates much like that of land mammals, requiring them to breathe air. They breathe through specialized nostrils called blowholes, located on top of their heads, which seal tightly when submerged. Breathing in whales is a conscious process, meaning they must actively decide to inhale and exhale.
Unlike humans who breathe automatically, whales remain partially awake even during rest to maintain control over their breathing and surface when needed. Their respiratory system is efficient, allowing them to exchange a large percentage of air with each breath and store oxygen in their blood and muscles for prolonged dives. If external factors prevent them from surfacing, or if water enters their blowholes, their mammalian physiology leaves them vulnerable.
Common Causes of Drowning
Entanglement in fishing gear is a frequent cause of whale drowning. Nets, lines, and other debris can wrap around a whale’s body, restricting its movement and preventing it from surfacing for air. These entanglements can lead to exhaustion, starvation, or severe injuries.
Collisions with vessels also contribute to whale drowning. Vessel strikes can inflict severe internal trauma, fractured bones, or deep propeller wounds that incapacitate the whale. Such injuries can prevent the animal from swimming effectively or surfacing to breathe, leading to drowning.
Environmental factors, such as extreme weather or rapidly forming ice, can also trap whales. In polar regions, sudden ice formation can cut off access to breathing holes, leaving whales with shrinking patches of open water. Whales can also drown if they become stranded in shallow waters where their blowholes are submerged by incoming tides.
Illness or severe injury can impair a whale’s ability to surface. Debilitating diseases, or injuries from predators, can weaken a whale to the point where it lacks the strength to swim or maintain buoyancy. Young calves are particularly vulnerable to predators, who may intentionally push them underwater. Underwater noise pollution, such as from sonar, can disorient whales, causing them to alter their diving patterns or strand themselves, which can indirectly lead to drowning.
Understanding Drowning Frequency
Quantifying the exact frequency of whale drowning incidents is challenging due to the vastness of the ocean. Many incidents occur far from human observation, and whale carcasses often sink before they can be discovered. Scientists primarily rely on stranding data and necropsies (animal autopsies) to gain insights into causes of death, including drowning. While not every whale death is attributable to drowning, it is a notable cause, particularly when linked to human activities.
Conservation and Mitigation Efforts
To reduce whale drownings, particularly those caused by human activities, various conservation and mitigation efforts are underway. Developing whale-safe fishing gear is one such effort, including “ropeless” systems that eliminate vertical lines that can entangle whales. Low breaking-strength ropes are also being developed, designed to break if a whale becomes entangled, allowing it to free itself.
Vessel speed restrictions are implemented in certain areas and times to reduce the risk of ship collisions with whales. For example, regulations may require ships to slow to 10 knots or less in designated whale habitats. Dynamic speed zones are also established when whales are observed in an area, encouraging mariners to reduce their speed.
Trained disentanglement teams play a role in rescuing whales already caught in fishing gear. These specialized teams use custom tools to cut away entangling lines, although such operations are dangerous and cannot save all affected animals. Establishing and managing marine protected areas (MPAs) helps safeguard important whale habitats, reducing overall human impact. Public awareness campaigns encourage reporting entangled or distressed whales, which can facilitate timely rescue efforts.